Electrolytic reduction of organic compounds by means of titanium compounds.



15 742 791 Patented October 27, 1903.

UNITED STATES PATENT EE CE.

MARTIN MOEST, HANS HERTLEIN, AND EHRICH OPPERMANN, OF HOCHST- ON-THE-MAIN, GERMANY, ASSIGNORS TO FARBWERKE, VORM. MEISTER, LUCIUS 85 BRUNING, OF HOCHST-ON-THE MAIN, GERMANY, A CORPORA- TION OF GERMANY.

ELECTROLYTIC REDUCTION OF ORGANIC COMPOUNDS BY MEANS OF TITANIUM COMPOUNDS.

SPECIFICATION forming part of Letters Patent No. 742,797, dated October 27, 1903. Application filed July 14. 1903. Serial No. 165,513. (No specimens.)

To whom it y Con/067"": salt having already become very considerable Beitknownthatwe,MAR'rINMOEsT,Ph.D., a kind of equilibrium sets in, when no fur- 5o HANS HERTLEIN,Ph. D., and EHRICH OPPER- ther reduction occurs. At this stage of the MANN, Ph. D., citizens of the Empire of Gerprocess the proportion of titano to titani salt 5 many, residing at Htichst-on-the-Main, Geris unaltered even if the current continues to many, have invented certain new and useful pass; but the proportion varies from the be- Improvements in the Reduction of Organic ginning, according to the conditions of the 55 Substances byMeans of Titanium Compounds electrolysis. If, however, a substance capain an Electrolytic Bath, of which the followbio of reduction is simultaneously introduced [0 ing is a specification. into this electrolytic cell-forinstance, finely- It is known by the experiments of Knecht divided azo-benzene-then the titano salt (Ber. d. d. Chem. Gas. 36, 166-169) that orformed at the cathode is at once reoxidized 6o ganic substances are most energetically reby the conversion of the azo-benzene into duced by titano salts. Thus titano chlorid benzidin, which is precipitated as sulfate.

reduces nitro compounds to amins, unsatu- The organic substance serves, so to say, rated acids to the corresponding saturated as acceptor (receiver) for the electrolytic acids, azo bodies are decomposed, 850. The hydrogen. In consequence of this the pro- 65 practical application of these compounds, portion of the titano salt compared with that however, has hitherto been impossible on acof the titani salt remains very small, so that count of their high price. the yield in relation to the current is favor- We now have found a process permitting able, although no diaphragm is used. a technical application of titano compounds We illustrate our process by the following 7: for reducing purposes in a simple and cheap examples: manner by conducting the reduction of or- Example I: A vessel lined with lead and ganic substances by means of titano com serving as cathode contains diluted sulfuric pounds in an electrolytic bath. Very small acid, with any quantity of titani sulfate-for portions only of the respective titanium cominstance, two per cent-dissolved in it. As 75 pound are requisite in the electrolyte, so that, anode may serve any first-class conductor in fact, the former is merely a carrier of the which is not attacked. The circuit is then electrolytic hydrogen. As the electrolyte closed and a concentrated solution of orthomay be used again in many cases, the quannitro-para-cresol-ortho-sulfonate of sodium is tity of titanium salt requisite, as well as the preferably introduced, with stirring, at a mod- 80 technical loss, is very little. In a great numerate temperature. This introduction is best ber of cases the reduction may also occur regulated in such a manner as to always leave without a diaphragm. This hitherto -unsome titano compound in the electrolyte. known fact is based on the following obser- Part of the amido compound formed is divation: rectly precipitated. The remainder is ob- 8 5 If a titani solution-for instance, a solution tained by concentrating the electrolyte. The of titani sulfate acidified with sulfuric acidwhole is then filtered, and the electrolyte may be electrolyzed in the absence of a diaphragm be used for another operation.

and with a lead cathode and platinum anode, Example II: The process of reduction may then the whole of the hydrogen at the cathof course occur also in the presence of a dia- 90 ode is first used to reduce the titani salt, phragm. This is particularly advantageous whereas the corresponding quantity of oxyif a simultaneous production of chlorin is degen escapes at the anode. The yield in resired. In this case the operation is, for inlation to the current is at first quantitative, stance, as follows: Fifty liters of hydrochloric but decreases in proportion as the contents acid of three-per-cent. strength containing a 5 of titano salt increases. Finally on the titano solution of about one to two per cent. of titanium chlorid are introduced into the cathodecompartment of a cell, one kilo of nitrobenzone and six hundred cubic centimeters of alcohol being stirred into it. The anode-compartment contains an acidified solution of common salt. As electrodes may be used almost all first-class conductors which are not essentially attacked. The process occurs suitably with heating and a density of current of three to six amperes per square meter. As soon as somewhat more than the theoretical quantity of current is used the process is'interrupted, and the anilin, which is obtained with excellent yield, is isolated in the usual manner.

Example III: The reduction of azo-benzene to benzidin may be carried out as follows: A vessel is used Example I. Lead, for instance, may be used as electrodes andasulfuric-acid solution ofsodium titanium sulfate as electrolyte. Finelyground azo-benzeue is then introduced into the liquid, heated to nearly the melting-point of the azo-benzene, and electrolyzed with a density of current of three to four amperes per square meter, the tension being three to four volts. Soon the benzidin sulfate is precipitated. On completion of the process it is filtered and converted into the free base in the usual manner, whereas the filtrate is reconducted into the electrolyzer.

In the foregoing example for azo-benzene may be substituted azo-o'xybenzene, which is also converted into benzidin. Like in Example II, a diaphragm may be used.

Example IV: If a quinone is to be reduced,

the operation m ay occur as follows: The cathode-compartment of a cell is filled with a so.- lution containing per liter twenty to thirty grams of hydrochloric acid, ten to twenty grams of titanium chlorid, and ten grams of benzo quinone. The anode compartment contains a solution of common salt. The

similar to that'described in 7 cathode is of lead, but may also consist of any other metal not essentially attacked. The process is conducted at ordinary temperature with a density of currentof one to two amperes per square meter and interrupted as soon as the odor of quinone has disappeared or somewhat more than the theoretical quantity of current is used. The hydroquinone, obtained with a good yield, is isolated in the usual manner for instance, with etherwhereupon the electrolyte may serve for another operation. 7 V

A great number of other organic substances may be reduced in a manner similar to that described in the above examples. Thus, for instance, from tetramethyldiamido benzophenone may be obtained the corresponding hydrol. In a similar manner nitroso compounds for instance, nitrosodimethylanilin,oximes, unsaturated acids, &c.are converted into their respective products of reduction,

The temperature, the proportions of quantity, and current of the above examples may be varied Within wide limits.

Having now described ourinvention, what we claim is The herein-described process for reducing organic substances by means of titanium compounds, which consists in conducting the reduction in an electrolytic bath in the presence of titanium compounds, substantially as set forth.

In testimony that we claim the foregoing as our invention we have signed our names in presence of two subscribing witnesses.

MARTIN MOEST. HANS HERTLEIN. EHRIOH OPPERMANN.

Witnesses ALFRED BRISBOIS, BERNHARD I LYDECKER. 

